The present invention relates to a linear actuator adapted to receive a removable tool and including the drive means for driving a movable component assembly for actuating the tool, controlled by an electronic module.
The invention is applicable to linear actuators, especially electro-mechanical actuators, designed for receiving a removable tool. The tool is actuated by a movable component assembly of the actuator. For example, such a tool is a tube working tool.
It is generally necessary to detect the arrival at the end of travel of the movable component assembly, as this may damage the actuator.
Patent FR-A-2 873 514 describes a linear actuator capable of receiving a removable tool, the tool being actuated by a screw driven in a translational movement, by an electric motor in both directions along its axis, designated by front and rear. This actuator includes sensors, in this case Hall effect sensors, for detecting the passage of a marker integrally attached to the screw, in this case a magnet, and for enabling the stop of the engine upon the screw reaching the end of travel in the front and/or rear directions.
Nevertheless, such an actuator does not give complete satisfaction. Indeed, the presence of the sensors results in additional manufacturing costs and increases the size and weight of the actuator.
An object of the invention is to provide an actuator having a reduced number of sensors.
To this end, the object of the invention relates to an actuator of the aforementioned type, in which the electronic module comprises the acquisition means for acquiring a variable that is representative of the instantaneous force supplied by the drive means and/or the time derivative of this variable, and in which the electronic module is capable of controlling the interruption means for interrupting the operation of the drive means if the said variable does not exceed a first predetermined value during a first predetermined time period from the start of the driving of the movable component assembly, and/or if the said derivative does not exceed a second predetermined value during the first predetermined time period from the start of the driving of the movable component assembly.
Indeed, the interruption of the operation of the drive means at the conclusion of the first predetermined time period prevents the bringing of the movable component assembly to the end stop position when no mechanical stress induced by the presence of a tool is detected.
According to particular embodiments, the invention presents one or more of the following characteristic features, taken into consideration individually or in accordance with any technically feasible combination:                the electronic module is capable of controlling the interruption means for interrupting the operation of the drive means if the said derivative does not exceed a second predetermined value during the first predetermined time period from the start of the driving of the movable component assembly.        the said drive means comprise an electric motor, and the said variable is the instantaneous intensity of the power supply current of the motor.        the electronic module comprises the means for automatically initiating operation of the said drive means at the conclusion of the a second predetermined time period after the interruption of their operation by the said interruption means, in order to bring back the movable component assembly into an initial rest position.        the actuator is powered by a battery.        the electronic module comprises the means for modifying the said first predetermined time period based on the level of charge of the battery.        